1. Field of the Invention
The present invention relates generally to an apparatus and method for controlling a transceiving device in a wireless terminal for a communication system. In particular, the present invention relates to an apparatus and method for controlling a transceiving gain level of a transceiving device in a wireless terminal for a communication system.
2. Description of the Related Art
Generally, a wireless terminal for use in wireless communication systems based on, for example, Code Division Multiple Access (CDMA) or Personal Communication Service (PCS) and various communication systems such as a Digital Multimedia Broadcasting (DMB) system, transmits and receives radio frequency (RF) signals to/from a base station via an antenna. For the signal transmission/reception, the wireless terminal comprises a transceiving device.
The transceiving device for the wireless terminal transmits and receives, for example, RF, Amplitude Modulation (AM), Frequency Modulation (FM), or Phase Modulation (PM) signals via an antenna. In most cases, the transceiving device comprises a transceiving matching block for adjusting intensity of transmission/reception signals.
FIG. 1 is a schematic block diagram illustrating a transceiving matching block included in a RF transceiving device. Referring to FIG. 1, an input signal received via an antenna ANT is applied to a controller 110 through a duplexer 110, a low-nose amplifier (LNA) 102, an RF amplifier 104, an intermediate frequency (IF) amplifier 106 and a receiver automatic gain controller (Rx AGC) 108. A transmission signal is transmitted through a transmitter automatic gain controller (Tx AGC) 112, an IF amplifier 114, a power amplifier (PA) 116, the duplexer 100 and the antenna ANT. The wireless terminal comprises the controller 110 for controlling gains of the LNA 102, the Rx AGC 108, the Tx AGC 112 and the PA 116 such that intensity of the received signal and intensity of the transmission signal can satisfy a predetermined level.
With the tendency toward diversity, complexity and multiplexing of the communication systems, there are various possible methods for controlling a transceiving device 120. For example, the transceiving device 120 is controlled by using a control signal. Alternatively, the transceiving device 120 is controlled by a separate serial interface included therein. In some cases, there is a need to control various gain levels in order to control the transceiving device 120.
In this manner, the transceiving device 120 has a structure for controlling a gain of the LNA 102 in an initial stage of a receiver and a gain of the PA 116 in a final stage of a transmitter by using several kinds of gain levels according to corresponding gain levels, and then controlling a fine gain level at an AGC amplifier. Conventionally, this structure has two kinds of gain levels of N and N+1.
With reference to FIG. 2A, a description will now be made of a method of controlling a gain of a transceiving device according to two kinds of gain levels. FIG. 2A is a block diagram illustrating a conventional gain level detection device for controlling a transceiving device 120 using two kinds of gain levels.
A signal intensity detector 200 detects a signal intensity value for an input signal received via an antenna. The signal intensity detector 200 outputs the detected signal intensity value to first and second comparators 202 and 204. The comparators 202 and 204 compare the received signal intensity value with a RISE N+1 value, which is a rising threshold, and a FALL N value, which is a falling threshold, respectively. The comparators 202 and 204 each output the results compared with the rising threshold and the falling threshold to a controller 110. Then the controller 110 detects a level state according to the comparison results, and generates a control signal for driving an amplifier of the transceiving device 120 within an appropriate operation range.
Although not illustrated in FIG. 2A, the gain level detection device comprises two timers for the two kinds of gain levels in order to provide timing hysteresis during level state transition. By providing the timers and setting timer values, it is possible to prevent a control circuit from unstably operating when the received signal intensity value rises and falls around the threshold. Of course, when there is no need for the timers, it is possible to operate the control circuit without timer setting.
FIG. 2B is an operation waveform diagram illustrating the gain level detection device of FIG. 2A.
For a gain level N, if a received signal intensity value is greater than or equal to a RISE value, the gain level detection device drives a timer by a timer setting value, in other words, drives a timer for the time indicated by a timer setting value. Thereafter, if the received signal intensity value is greater than or equal to the RISE value when the timer expires, the gain level changes to N+1. Thereafter, for a gain level N+1, if a received signal intensity value is smaller than or equal to a FALL value, the gain level detection device drives a timer by a timer setting value. Thereafter, if the received signal intensity value is smaller than or equal to the FALL value when the timer expires, the gain level changes to N.
FIG. 2C is a state transition diagram illustrating the gain level detection device illustrated in FIG. 2A.
If a received signal intensity value is smaller than or equal to a RISE value, the gain level detection device stays in an N state. If the received signal intensity value becomes greater than the RISE value and the received signal intensity value is greater than the RISE value until a timer expires in an N+1 wait state, the gain level detection device transitions to an N+1 state. If the received signal intensity is greater than or equal to a FALL value, the gain level detection device holds the N+1 state. In the meantime, if the received signal intensity value becomes smaller than the FALL value, the gain level detection device goes to the N state. Thereafter, if the received signal intensity value is smaller than the FALL value until a timer expires, the gain level detection device transitions to the N state. In the case where no timer is used, if the received signal intensity value is greater than or equal to the RISE value in the N state, the gain level detection device immediately transitions to the N+1 state, and if the received signal intensity value is smaller than or equal to the FALL value in the N+1 state, the gain level detection device immediately transitions to the N state.
FIG. 3A is a block diagram illustrating a gain level detection device for controlling a transceiving device with four kinds of gain levels to control the transceiving device having a plurality of gain levels by extending the 2-level state-based gain control of FIG. 2A.
To control four kinds of gain levels, the gain level detection device requires six comparators 302, 304, 306, 308, 310 and 312, and six timers when timers are used. That is, referring to FIG. 3B, because there are six thresholds of a FALL N value, a RISE N−1 value, a FALL N+1 value, a RISE N value, a FALL N+2 value and a RISE N+1 value for transition to gain levels of N−1, N, N+1 and N+2, to be compared with a received signal intensity value, the gain level detection device requires six comparators.
As a result, the number of comparators and timers increases with the number of gain levels for controlling a gain of the transceiving device. That is, in the structure for controlling a gain of the transceiving device according to a plurality of gain level states, the number of required comparators and timers depends on the number of gain level states for gain control.
Therefore, an increase in number of the gain level states increases the required number of comparators and timers included in a wireless terminal, causing an increase in complexity or size of the wireless terminal. In some cases, the number of logics can be reduced to some extent through timing sharing or structure sharing design, but the increase in the overall hardware complexity due to the additional logics is considerable.
In addition, in the case of designing the hardware with a fixed gain level, its flexibility decreases due to the fixing of the supported gain level during a compatibility test actually applied to the transceiving device or when the transceiving device is replaced with a new one.